<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<style>
    div{
        width: 200px;
        height: 200px;
        border: 1px solid black;
        display: flex;
        justify-content: center;
        align-items: center;
    }
</style>
<body>
    
<div>
    这是内容
</div>

</body>
<script>
  
</script>
</html>